In the packing or packaging sector, plants are known which are used to make containers by means of a plurality of operations on a packaging material, for example a sheet of cardboard.
Known plants generally comprise a plurality of machines operatively disposed in series, and each of which is provided with a support structure substantially transverse to the direction of feed of the sheet.
One type of machine provided in such plants comprises at least a cutting and/or pre-creasing unit having a pair of operating heads, each of which supports, moves and commands both a cutting tool and a pre-creasing tool.
Solutions are known whereby the cutting and/or pre-creasing unit has tools suitable to operate both in a transverse direction to the direction of feed of the sheet, and also in a longitudinal direction to the direction of feed of the sheet.
In some cutting and/or pre-creasing conditions one and/or the other tool of each operating head can remain unused, limiting the potential productivity of the machine.
Such known plants are little suited for production in small series, and need long fitting out times to change to producing series which are different from each other.
Moreover, since in the known machines the tools are provided in pairs for each operating head, possible parallel operations distanced only a few millimeters from each other are difficult to carry out, possibly causing operational inaccuracies.
US-A-2009/0062098 discloses a creasing device for forming creases in corrugated or cardboard sheets, comprising a plurality of creasing units of the sheet, suitable for executing longitudinal creases on the sheet in a direction longitudinal with respect to the feeding direction of the sheet, and in which the distance between upper female roller and lower male roller of each creasing unit is individually adjustable. Four creasing units are movable each other along a direction transversal to the feed direction of the sheet, while a central creasing unit is disposed fixed on an upper stationary frame. Moreover, the creasing device of US'098 comprises a plurality of grooving units, disposed spaced apart one each other in a fixed manner with respect to the feeding direction and downstream of the creasing units, for executing slots on the sheet in a direction longitudinal with respect to the feeding direction of the sheet. Four grooving units are movable each other along a direction transversal to the feed direction of the sheet, while a central grooving unit is disposed fixed on a lower stationary frame.
WO-A-2005/09697 discloses a machine for manufacturing cardboard blanks from a cardboard portion including a feeding assembly for moving the cardboard portion, a first operating head disposed above the feed plane of the cardboard blank, fit to execute workings on the cardboard in a transversal direction with respect to the moving direction of the cardboard, and which is mobile in a direction orthogonal to the moving direction of cardboard portion and driven by first actuator means and second operating heads fit to execute workings on the cardboard in a longitudinal direction with respect to the moving direction of the cardboard and disposed above the feed plane of the cardboard blank, downstream the first operating head and each independently positionable by means of second actuator means in a transversal direction with respect to the machine.
Purpose of the present invention is to achieve a machine and a unit, and to perfect a method, for cutting and/or pre-creasing, which are suitable for small productions, which allow to exploit to the maximum the potential productivity of the machine and which are less bulky, more accurate and cost less.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.